Driven proportional-control thermostatic device with back-up thermostatic element

ABSTRACT

The invention relates to a device of the valve type comprising a housing having a fluid access ( 7 ) which is shut off by a shutter ( 9 ) secured to an actuator ( 10 ) as a function of the temperature of the fluid passing through the device.  
     In order to improve its operational dependability, and reduce its cost, the device comprises an expanding-material back-up thermostatic element ( 22 ) lying in the stream of fluid passing through the housing, to actuate the shutter ( 9 ) when, as a result of defective operation of the actuator ( 10 ) or of its control gear, the shutter has not been moved by the actuator, which also consists of an expanding-material thermostatic element containing heating means ( 13 ) connected to its control gear.

[0001] The invention relates to a thermostatic device of the valve type with a proportional-control actuator, comprising a thermostatic element which may be a conventional expanding-wax thermostatic element, to also give it a back-up mode of operation if the actuator or its control gear should prove defective.

[0002] Thermostatic devices of the valve type are used, for example, in internal combustion engine cooling circuits for regulating the temperature of the cooling liquid (generally an aqueous mixture known as “coolant”) introduced into the engine in order to optimize its operation by acting on a flow of “hot” liquid coming from the vehicle engine and/or a flow of “cold” liquid coming from a cooling radiator, which are mixed to form a “warm” cooling liquid which is reintroduced into the engine.

[0003] It should be noted that the words “hot”, “cold” and “warm” are used with a view to simplifying the vocabulary to indicate relative temperature levels of the three streams of liquid when the device is operating in steady state, but that in fact the respective temperatures of these three streams may be very similar, and may even be identical when the thermostatic device is still closed.

[0004] Thermostatic devices motorized by means of an electric motor comprising a back-up thermostatic element, for example making it possible, inside a chamber of the device, to mix a stream of cold liquid with the stream of hot liquid even when the engine or its control gear are defective, if the temperature of the liquid in which the thermostatic element is immersed exceeds a desired value, are already known, particularly from the French patent published under the number 2 703 730.

[0005] The thermostatic device in that document 2 703 730 is motorized by means of an electric motor comprising a rotary output shaft actuating the moving shutter of the thermostatic device by means of a conventional screw-nut coupling system that converts the rotary movement of the shaft into a translational movement, this moving shutter being namely a spool or “plug” gradually uncovering a cold liquid inlet access of this device at the same time as it gradually shuts off a hot liquid inlet access, and vice versa; the back-up thermostatic element is aligned with the screw of the screw-nut system and when its temperature rises, its piston exerts on the plug, if the latter has not been moved or has not been moved far enough by the screw-nut system, a force oriented in the direction of uncovering the cold liquid inlet access and of shutting off the hot liquid inlet access so that under the thrust of the piston of the thermostatic element, the spool can actually move in that direction, the screw-nut system coupling is telescopic and, more specifically, mounted so that it can slide on the shaft of the motor, urged by a spring towards the plug in the direction of uncovering the hot liquid inlet access and of shutting of the cold liquid inlet access; thus, when the thermostatic element exerts on the plug a force in the opposite direction which is higher than that of the spring, in order to shut off the hot liquid inlet access and uncover the cold liquid inlet access, the spring is compressed by the retraction of the screw-nut system and there is then nothing to prevent this respective shutting-off and uncovering.

[0006] Beside the fact that this device is of the plug valve type, a configuration which is sometimes difficult to tailor to certain engine and cooling circuit structures, one disadvantage of this device consists of the fact that when the temperature of the liquid in which the thermostatic element is immersed decreases, the screw-nut system accompanies the retracting movement of the thermostatic element which, because the electric motor or its control gear is defective, leads to a further rise in temperature, a further elongation of the thermostatic element, and an operation which tends towards instability with “warm” liquid at a temperature appreciably higher than the desired temperature. In addition, the thermostatic element has to be relatively powerful in order to overcome the resistive force of the spring, and the screw-nut system with its telescopic spring-loaded mounting is relatively bulky, which means that the dimensions of the thermostatic device cannot be reduced as far as might be wished.

[0007] It is an object of the invention to overcome these drawbacks, and the invention therefore relates to a thermostatic device comprising a housing comprising fluid accesses, it being possible for at least one fluid access to be shut off by a shutter, a metering actuator fixed to the housing and equipped with an output stem that can move in translation and is mechanically connected to the shutter in order to actuate this shutter in terms of translation selectively in a direction in which it gradually shuts off the access that can be shut off and in a direction in which it gradually, as a function of at least one engine operating parameter detected by at least one sensor, uncovers it, and a back-up thermostatic element situated at least partially in the stream of fluid and comprising a part designed to actuate the shutter in translation when, as a result of defective operation, the latter has not been actuated by the metering actuator and the temperature of the said stream of fluid exceeds, by a predetermined value, the temperature which should have given rise to such actuation by this actuator, characterized in that the metering actuator is a proportional-control actuator consisting of an expanding-material thermostatic element also containing heating means associated with means of connecting the heating means to control gear involving a computer connected to the said sensor, via which the metering actuator is driven through the connecting means.

[0008] By virtue of the fact that the proportional-control metering actuator is a thermostatic element designed to be heated at the command of a computer, rather than an electric motor such as a stepping motor, the cost price of the thermostatic device is appreciably lowered.

[0009] Furthermore, if this device with two thermostatic elements is compared with the earlier devices with two thermostatic elements which had a metering thermostatic element, the expanding material of which was heated only by the fluid passing through the housing and which also had a thermostatic element for adjusting the threshold at which regulation began, which could be heated or not at the command of a computer, it can be clearly demonstrated that the device according to the invention makes it possible to obtain a vehicle engine operating temperature which is always optimum from the two points of view which are fuel consumption and pollutant emissions, irrespective of the load on this engine.

[0010] The thermostatic device may also exhibit one or more of the following features:

[0011] the heating means comprise a resistive electrical component, and the connecting means are electrical conductors designed to connect the resistive component to the control gear comprising the said vehicle on-board computer;

[0012] the back-up thermostatic element is set to actuate the shutter in the direction of opening for a fluid temperature a few degrees higher than the temperature at which the metering actuator is set for actuating the shutter in that direction;

[0013] the metering thermostatic element is arranged in the housing downstream of the access that can be shut off by a shutter;

[0014] the metering thermostatic element is carried by a support extending into a duct belonging to the housing;

[0015] the metering thermostatic element and the back-up thermostatic element are arranged one on each side of the access that can be shut off, the metering thermostatic element has an output stem which can move in terms of translation and projects towards the shutter, the back-up thermostatic element has a piston, also projecting towards the shutter and facing the output stem, and the piston is fixed to the output stem;

[0016] the back-up thermostatic element has a collar housed at least partially in a skirt of the shutter;

[0017] the device comprises a return spring resting against the shutter to exert on it a force that tends to return it in the direction of closing; and

[0018] the output stem and the piston are secured together with the interposition of a thrust washer designed to be able to rest selectively, at the end of travel, against the free end of a ring of the metering element and against the free end of a ring of the back-up element.

[0019] Other features and advantages of the invention will become apparent from the description which will follow, of one embodiment of the invention given by way of non-limiting example, illustrated by the appended drawings in which FIGS. 1 and 2 show diagrammatically, in section, a thermostatic device according to the invention respectively in a condition in which the moving shutter of the device is subjected to the action of the metering actuator when the latter and/or its control gear is or are not defective, and in a condition in which, as the actuator and/or its control gear is or are defective, the back-up thermostatic element has taken over to actuate the moving shutter.

[0020] In order not to overload the drawing, a certain number of components and of lines relating to components which are behind the planes of section have not been depicted in the figures, but the arrangement of the device according to the invention will be made easier to understand by the description which will follow.

[0021] The thermostatic device depicted comprises, in the known way, various members housed in a housing generally made of synthetic material, formed of a duct or pipe 1, in this instance straight, but which may be elbowed, carrying fingers 2 housed in a body 3 consisting of a region of a vehicle engine surrounding a passage 4 through which the engine cooling liquid passes, which passage is hollowed out in this region and at which one or more conduits for the circulation of fluid, such as a cooling liquid, terminate. The duct 1 is externally equipped with a fixing flange 5 via which it is fixed to the body, for example by screws; the region of its opposite free end to its end region which has the fingers 2 is designed for another duct such as a hose to be attached to it.

[0022] In this case, the duct 1 and the passage 4 have an axisymmetric overall shape with a cross section at right angles to the axis which is approximately circular and they run, in alignment, along one and the same central longitudinal axis, in a first direction.

[0023] The region of the housing running into the passage 4 has at least one first, fluid inlet, access 6 for fluid coming from the engine, and a second, fluid outlet, access 7 for transmitting in the downstream direction some of the fluid which is intended to be recirculated, generally by means of a water pump.

[0024] The first, fluid inlet, access 6 lies near the free end of the fingers 2, and the second, fluid outlet, access 7 is delimited by the end region of the duct 1 to which the fingers are connected; at this second access 7, the interior surface of the duct 1 has a frustoconical shape widening towards the first access to constitute a seat 8 for a shutter which here consists of a shutter element 9 for metering the fluid allowed to flow through the passage 4 to the duct 1.

[0025] The region of the housing that runs between the first access 6 and the seat 8 will hereafter be referred to as the “upstream region” of the housing, while the region which runs beyond the seat 8 into the duct 1 towards the free end thereof will be termed the “downstream region” of the housing.

[0026] In order to actuate the shutter element 9 in translation selectively in a direction in which it gradually shuts off the fluid outlet access 7 and in a direction in which it progressively, particularly as a function of the temperature of the stream of cooling fluid passing through the thermostatic device detected by a sensor CT1 immersed in this stream approximately at the first access 6, uncovers it, the device comprises a metering actuator 10 fixed to the housing and equipped with an output stem 11 mechanically connected to the shutter element 9.

[0027] More specifically, the metering actuator 10 is a linear motor consisting of a thermostatic element containing an expanding material 12 such as expanding wax and also containing means for heating this material, for example a resistive electrical component 13, which are associated with connecting means 14 for connecting these heating means to control gear designed to cause the thermostatic element to operate as a proportional-control linear motor; more specifically, in this case, the electrical power supplied to the thermostatic element 10, and so the travel of the stem 11, is proportional to the difference between the measured temperature of the fluid and a programmed-in reference temperature; control may also be integral (proportional action at the “surface” of the difference) and/or derivative (partial compensation for dead times); it is also possible to envisage the use of “fuzzy logic”.

[0028] The resistive electrical component 13 may be a simple electrical resistor or a helix-wound resistor known commercially by the name of THERMOCOAX, or a resistor printed onto an insulating wafer, or alternatively a resistive rod, or a thermistor known in the art by the name C.T.P.; the connecting means 14 are then electrical conductors connected to the resistive component 13.

[0029] The thermostatic element constituting the metering actuator 10 is carried by an elbowed tubular support 15 made of a single piece with the housing and running inside the latter in its downstream region. The tubular support 15 opens to the outside of the duct 1 via an orifice pierced in the side wall thereof, and to the inside of the duct via a circular orifice centred on the central longitudinal axis common to the duct 1 and to the passage 4 and opening towards the seat 8. The support 15 thus has a first portion running in the first direction defined above as being that of the aforementioned longitudinal axis, in which the envelope 16 of the thermostatic element is fixed, and a second portion running in a second direction at right angles to the first direction in the particular instance in which the duct 1 is not elbowed, and in which in this instance a grommet 17 is fixed for the passage of the electrical conductors which constitute the connecting means 14; as an alternative, the second portion may be used for fixing an electrical connector to which the conductors 14 are connected.

[0030] The resistive component 13 is fixed at one of its ends into an end region of the envelope 16 inserted in the first portion of the support 15, and the greater part of its length runs into the mass of expanding material 12; the opposite end region of the envelope 16, the greater part of the length of which extends into the duct 1 outside the support 15, comprises a collar 18 in which is crimped a ring 19 forming a guide support for the output stem 11 which passes slidingly through it and to which is fixed a deformable tubular cap 20 lodged in the mass of expanding material contained in the envelope 16, into which cap the region of the output stem 11 that runs inside the envelope is inserted; by contrast, it is the region of the output stem 11 which projects out of the envelope 16 and of the ring 19 towards the shutter element 9 which is connected mechanically to the latter in order to actuate it in translation.

[0031] The operation of the thermostatic element 10 is controlled by the gear comprising a computer 21 which may be the vehicle on-board computer or may be a separate computer, receiving information about the temperature T1 of the cooling fluid, transmitted to it by the sensor CT1 immersed in the stream of fluid as already mentioned, upstream of the seat 8 for the shutter element, and possibly also information about the air temperature T2 at the engine inlet, and/or information about the vehicle speed, and/or information about the engine load, and/or information about the external temperature, which items of information are transmitted to it by appropriate sensors. In order to slave or at least drive the thermostatic element 10 using the computer control gear, the computer 21 is connected to the element 10 directly by the connecting conductors 14 or through any conductor that might be fixed into the support 15.

[0032] The thermostatic device according to the invention further comprises a back-up thermostatic element 22 also containing an expanding material 23 which is an expanding wax, but without internal heating means and the envelope 24 of which is immersed in the cooling fluid passing through the upstream region of the housing; this back-up element 22 is arranged in line with the metering element 10, that is to say that like it, it is centred on the central longitudinal axis of the duct 1 and of the passage 4, but in opposition with the metering element, the closed end of its envelope 24 being approximately in line with the free end of the fingers 2, and its ring 25 forming a guiding support for a piston 26 being approximately level with the shutter element 9.

[0033] More specifically, the end region of the envelope 24 near the bottom thereof is centred between the fingers 2 through the fact that it is mounted to slide in a hole in the central part of a bridge element 27 carried by the fingers 2 and running in the upstream region of the housing; for this purpose, the bridge element 27 has branches projecting radially towards the fingers 2, the free ends of which branches are housed in respective notches 28 of the fingers near the free end thereof and are in abutment against bottom surfaces of these notches which run at right angles to the longitudinal axis of the housing, under the action of a helical spring 29; this spring, surrounding the back-up element 22, rests at one of its ends against the branches of the bridge element and, at the opposite end, against the shutter element 9.

[0034] The shutter element 9 comprises a bearing annulus 30 made of synthetic material which, facing the seat 8, has an approximately frustoconical surface of a diameter that increases towards the fluid inlet access 6, and which is designed to rest against the seat 8 when the shutter element is in the closed position, and a metallic reinforcement 31 in the form of a dish with a circular periphery, the periphery region of which is inserted in the interior surface of the bearing annulus 30. The central regions of the bridge element 27 and of the metallic reinforcement 31 surrounding the envelope 24 of the back-up element 22 comprise, facing each other, respective approximately cylindrical skirts for centring the helical spring 29 around the envelope.

[0035] At its opposite end to its bottom near the free end of the fingers 2, the envelope 24 has a collar 32 in which is crimped the ring 25 through which the rod of the piston 26 passes, which rod is mounted to slide in the ring and to which is also fixed a deformable tubular cap 33 housed in the mass of expanding material contained in the envelope 22, into which cap the region of the rod of the piston 26 extending into the envelope is inserted. The collar 32 is housed at least partially in the skirt 34 of the metallic reinforcement 31, and the surface of its shoulder for connecting to the cylindrical part of the envelope containing the expanding material, which extends in a plane perpendicular to the longitudinal axis of the housing, rests against the bottom of the skirt of the metallic reinforcement 31.

[0036] The mechanical connection between the metering element 10 and the back-up element 22 with the shutter element 9, allowing, in normal operation, proportional actuation of the shutter element by the metering element under the control of the gear involving the computer, and, in the event of defective operation of the metering element 10 and/or its control gear, actuation of the shutter element by the back-up element, will now be described.

[0037] This connection is extremely simple because all that is required is for the output stem 11 of the metering element and the piston 26 of the back-up element to be fixed together with the interposition of a thrust washer 35 projecting annularly with respect to the stem 11 and to the piston 26 and intended, at the end of travel, to rest selectively against the free end of the ring 19 of the metering element and against the free end of the ring 25 of the back-up element. For example, the stem 11 at its free end has a threaded finger and the piston 26 at its free end has a tapped hole into which this threaded finger, around which the thrust washer 35 is slipped, is screwed.

[0038] Thus, the flow of the cooling liquid can be regulated according to the temperature of the water circuit, the air inlet temperature, the vehicle speed, the engine load and the external temperature, by moving the shutter element 9 away from the seat at will. The flow and the temperature in the water circuit can be set to the optimum value for obtaining maximum consumption saving and minimum pollution for each phase in the operation of the engine regardless of the load thereon. More specifically, the thermostatic device according to the invention and its control gear can be set so that, when the gearbox is in a given gear, the voltage applied to the metering element 10 follows the variations in vehicle speed and maintains a cooling fluid temperature at the outlet of the engine which is approximately constant, for example within a 4° C. range. When the cooling fluid temperature sensor detects that the amount by which optimum temperature is exceeded is greater than a predetermined value, suggesting defective operation of the metering element 10 or of its control gear, the back-up element 22 positioned upstream of the shutter element 9 moves the latter to a distance which is itself predetermined according to an algorithm in the computer which takes account of the information delivered by the other sensors. The value of the threshold at which the back-up element 22 comes into operation can be chosen, for example, in a range from 2° C. to 5° C. higher than the ideal set temperature for high temperatures. For example, in the case of an ideal temperature of 100° C. to 102° C., it may be possible to choose a temperature of 104° C. for the temperature at which the back-up element begins to open, and a temperature of 110° C. at which it is wide open.

[0039] Alarm equipment may be connected to the computer to let the driver of the vehicle know if it becomes impossible to set to the ideal temperature, in which case the vehicle will have to be taken to a workshop where the cooling circuit can be checked out, adjusted and, if necessary, repaired.

[0040] By virtue of the fact that the metering element 10 is downstream of the shutter element 9, the reaction time on the opening of the shutter element at the time of its first opening in operation, is shortened.

[0041] By virtue of the fact that this element is a thermostatic element heated under the control of a computer, operation similar to that of a thermostatic device with stepping motor and reversible screw is obtained, hence an appreciably less complex set-up for an appreciably lower cost.

[0042] Of course, the invention is not restricted to the form of embodiment described hereinabove and depicted, and others may be envisaged without departing from its scope. 

1. Thermostatic device comprising a housing comprising fluid accesses (6, 7), it being possible for at least one fluid access (7) to be shut off by a shutter (9), a metering actuator (10) fixed to the housing and equipped with an output stem (11) that can move in translation and is mechanically connected to the shutter in order to actuate this shutter in terms of translation selectively in a direction in which it gradually shuts off the access (7) that can be shut off and in a direction in which it gradually, as a function of at least one engine operating parameter detected by at least one sensor (CT1), uncovers it, and a back-up thermostatic element (22) situated at least partially in the stream of fluid and comprising a part (32) designed to actuate the shutter in translation when, as a result of defective operation, the latter has not been actuated by the metering actuator and the temperature of the said stream of fluid exceeds, by a predetermined value, the temperature which should have given rise to such actuation by this actuator, characterized in that the metering actuator (10) is a proportional-control actuator consisting of an expanding-material thermostatic element also containing heating means (13) associated with means (14) of connecting the heating means to control gear involving a computer (21) connected to the said sensor (CT1), via which the metering actuator is driven through the connecting means.
 2. Thermostatic device according to claim 1 for a vehicle equipped with an on-board computer, characterized in that the heating means (13) comprise a resistive electrical component, and the connecting means (14) are electrical conductors designed to connect the resistive component to the control gear comprising the said vehicle on-board computer.
 3. Thermostatic device according to claim 1, characterized in that the back-up thermostatic element (22) is set to actuate the shutter (9) in the direction of opening for a fluid temperature a few degrees higher than the temperature at which the metering actuator (10) is set for actuating the shutter in that direction.
 4. Thermostatic device according to claim 1, characterized in that the metering thermostatic element (10) is arranged in the housing downstream of the access (7) that can be shut off by a shutter (9).
 5. Thermostatic device according to claim 1, characterized in that the metering thermostatic element (10) is carried by a support (15) extending into a duct (1) belonging to the housing.
 6. Thermostatic device according to claim 1, characterized in that the metering thermostatic element (10) and the back-up thermostatic element (22) are arranged one on each side of the access (7) that can be shut off, the metering thermostatic element (10) has an output stem (11) which can move in terms of translation and projects towards the shutter (9), the back-up thermostatic element (22) has a piston (26), also projecting towards the shutter and facing the output stem (11), and the piston (26) is fixed to the output stem (11).
 7. Thermostatic device according to claim 6, characterized in that the back-up thermostatic element (22) has a collar (32) housed at least partially in a skirt (34) of the shutter (9).
 8. Thermostatic device according to claim 6, characterized in that it comprises a return spring (29) resting against the shutter (9) to exert on it a force that tends to return it in the direction of closing.
 9. Thermostatic device according to any one of claims 6 to 8, characterized in that the output stem (11) and the piston (26) are secured together with the interposition of a thrust washer (35) designed to be able to rest selectively, at the end of travel, against the free end of a ring (19) of the metering element (10) and against the free end of a ring (25) of the back-up element (22). 